This invention relates generally to gas delivery systems and, more particularly, to a system for delivering oxygen which includes an oxygen conserving device or oxygen conserver.
Gas delivery systems typically include a source of gas, such as oxygen, a regulator for reducing the source pressure of the oxygen to a pressure more suitable for use within the delivery system, and a gas line, typically a cannula, for delivering oxygen from the delivery system to the person. Oxygen delivery systems are used not only in hospitals and health care institutions, but also in home-health care and by ambulatory persons requiring oxygen for any number of reasons. Wherever such oxygen delivery systems are used, it is frequently desirable to increase the life of the oxygen supply. This is especially the case in home-based or ambulatory settings where the supply of oxygen is often an oxygen bottle or other relatively finite oxygen source.
To increase the life of the oxygen supply, oxygen conserving devices, also known as oxygen conservers, are frequently used. These conserving devices generally interrupt the flow of oxygen delivered to the person at regular intervals, thereby reducing the rate of oxygen consumption.
Conservers are generally of two types, those which operate electronically, and those which operate pneumatically. Each of these types suffers from various drawbacks and disadvantages. For example, electronic conservers require a power source, generally a battery, in order to operate, thus necessitating periodic replacement or recharging of the power source.
Electronic oxygen conservers sometimes have further disadvantages related to durability and cost.
Pneumatic oxygen conservers are those which make use of the pressurized gas and its flow within the conserver to intermittently block the delivery of as to the person. Although such pneumatic conservers generally dispense with the need for power sources and complex electronics, they are oftentimes bulkier.
A further disadvantage of pneumatic systems is that they generally require more complex gas lines or cannulas in order to operate. Examples of such pneumatic conservers and their associated dual-lumen cannulas are disclosed in Myers U.S. Pat. No. 5,044,133 and Carter U.S. Pat. No. 5,360,000. One lumen of the cannula is for supplying oxygen to the person wearing the cannula, whereas the other lumen generally connects to a sensing port on the conserver. The pneumatic conserver generally responds to changes in the pressure in the sensing lumen to provide oxygen to the person during inhalation and to interrupt the flow of oxygen to the person in response to exhalation (when oxygen is typically not needed). Unfortunately, dual lumen cannulas are more difficult to obtain, more expensive, bulkier, and generally heavier than the standard, single lumen cannulas used in electronic conservers and many other medical devices.
As a result of these and other drawbacks, pneumatic oxygen conserving devices have not enjoyed widespread use despite certain advantages of such pneumatic conservers over electronic ones.
The various attempts to overcome the drawbacks of pneumatic conservers have had mixed results and have generated their own drawbacks and disadvantages. For example, although the pneumatic oxygen conserver disclosed in Hoffman U.S. Pat. No. 5,881,725, makes use of a single-lumen cannula, the device disclosed therein does not generally deliver oxygen in a manner consistent with the oxygen consumption profiles of a person breathing through a cannula. In other words, it is desirable for oxygen delivery from a conserving device to match a person""s needs for oxygen as closely as possible.
There is a need, therefore, for a pneumatic oxygen conserving device which can be used as part of an oxygen delivery system, and which overcomes the disadvantages of current oxygen delivery systems.
According to one aspect of the invention, a conserving device includes a reservoir which holds a volume of gas for delivery to the person to receive the gas. A delivery system opens and closes an outlet to the reservoir to dispense the gas intermittently. A sensing system detects a pressure drop resulting from inhalation by the person and, as a result of such detection, the sensing system causes the delivery system to open the reservoir outlet. Such opening of the reservoir dispenses the volume of gas from the reservoir and ultimately to the patient. A gas control system is connected to receive gas from the source and from the delivery system the gas control system is connected to the sensing system in such a way that, when the gas control system receives the gas from the delivery system, pressure in the sensing system is increased. The gas control system is further connected to the delivery system to cause the delivery system to close the outlet to the reservoir, in response to increased pressure in the sensing system.
According to another aspect of the present invention, a conserving device includes a reservoir which receives gas from a gas source. A main valve operates to open the reservoir to discharge gas contained therein and to close the reservoir to repressurize it. A pressure line extends from the source of gas to the main valve and biases the main valve toward the closed position. The pressure line also is connected to a sensing valve through a port. The sensing valve is pneumatically connected to a vent to atmosphere and also to a delivery outlet of the device. The delivery outlet is adapted to connect to the gas line. A sensing passage is disposed between the delivery outlet and the sensing valve. When a person inhales, the inhalation is transmitted to the delivery outlet through the gas line. The sensing passage permits air to be drawn from one side of the sensing valve, which then opens the port. When the port opens, gas from the pressure line escapes through the orifice and out the vent to atmosphere. The venting of the gas to atmosphere reduces the biasing of the main valve so that it opens the outlet of the reservoir. Gas discharges from the now open reservoir and exits through the delivery outlet, through the gas line and to the patient. The sensing passage is located relative to the delivery outlet in such a way that some of the gas being delivered passes back through the sensing passage. This returning gas creates sufficient pressure to close the sensing valve, whereupon gas from the pressure line no longer escapes through the vent. Instead the gas from the pressure line closes the main valve to close the reservoir outlet, interrupting delivery of the gas to the patient and permitting repressurizing of the reservoir. In this way, pulses of gas are delivered intermittently and gas is conserved.
In accordance with another aspect of the invention, an orifice plate is included in the device and has a set of vent orifices, a selected one of which is interposed in the vent to atmosphere. In still another version of the invention, the orifice plate includes a set of orifices of varying sizes, each orifice corresponding to a rate of flow of the gas.
In yet another aspect, the invention comprises a pneumatic apparatus for gas delivery through a single-lumen cannula. The apparatus has components housed in a main body, such components including a regulator, a flow-rate selector, a reservoir for receiving gas therein at varying pressures, a main valve movable to open and close the reservoir, a sensing valve responsive to inhalation transmitted through the cannula; a delivery outlet connected to the cannula, and a sensing passage between the delivery outlet and the sensing valve.
The main body includes a plate therein, and the plate is structured to form the reservoir, the main valve, and at least one passage from the main valve.
In one version of the invention, the plate, the regulator, and the flow rate selector are secured to each other along the longitudinal axis of the main body and are substantially cylindrical.
The invention will be better understood by reference to the attached drawing. It is understood that the drawing is for illustrative purposes only and is not necessarily drawn to scale. In fact, certain features of the drawing are shown in more detail for purposes of explanation and clarification. In the drawing:
FIG. 1 a side elevational and partly schematic view of an apparatus for delivering oxygen according to the present invention;
FIG. 2 is a top plan view of the oxygen conserving device of the apparatus shown in FIG. 1;
FIG. 3 is an exploded perspective view of the conserving device of FIG. 2;
FIG. 4 is a cross-sectional view of the conserving device taken along line IVxe2x80x94IV of FIG. 2;
FIG. 5 is a cross sectional view taken along line Vxe2x80x94V of FIG. 1;
FIG. 6 is a cross sectional view taken along line VIxe2x80x94VI of FIG. 2;
FIGS. 7 and 8 are perspective and top plan views, respectively, of one of the components of the conserving device of FIGS. 2 through 6;
FIGS. 9 and 10 are two side views of the component of FIGS. 7 and 8;
FIGS. 11, 12, and 13 are top, bottom, and side sectional views, respectively, of another component of the oxygen conserver of the present invention; and
FIG. 14 is a graph of the operation of the device according to the present invention.